In the drilling of wells, such as oil or gas wells, core samples of porous rock are taken of the earth formation through which the wells are drilled and various characteristics of the rock are determined for the purpose of establishing different fluids in the formation, estimating the quantity of each fluid in the formation, the ease of flow through the formation, etc. Such core samples are also taken from producing reservoirs and characteristics of the rock are determined for the purpose of estimating particular fluid quantities, predicting production rates, etc. Particularly important among the characteristics of the porous rock commonly determined is wettability.
Many different methods of measuring wettability have been utilized, see "Wettability Literature Survey--Part 2: Wettability Measurement", Journal of Petroleum Technology, November 1986, pgs. 1246-1262, by William G Anderson. The quantitative wettability measurements include contact angles, imbibition and forced displacement, and USBM wettability method. Other wettability measurements include imbibition rates, microscope examination, flotation, glass slide method, relative permeability curves, permeability/saturation relationships, capillary pressure curves, capillarimetric method, displacement capillary pressure, reservoir logs, NMR and dye adsorption.
It is a specific object of the present invention to provide a new method for quantitatively measuring the degree of wettability of porous rock from a core sample taken from a subterranean formation as an indication of the formation's potential for oil or gas production.